The present invention generally concerns analog metering devices having moving needles. The invention is particularly suitable as an add-on accessory to a speedometer or a tachometer. The invention also concerns secondary devices that rely upon or may use information obtained from an add-on accessory monitoring a set critical value of an analog metering device. Another field of the invention is radar detectors that monitor radar for use in motor vehicles.
Speedometers, tachometers, and similar devices provide critical information to drivers of motor vehicles. Use of the information provided by such an instrument, however, requires an operator to divert attention away from the environment in which the vehicle is being operated. Although only momentary, it is better that an operator rarely, if ever, need to divert attention away from the environment since reference of the environment surrounding the motor vehicle is critical to safety of operation.
Various devices have been previously developed to address this general concern. Cruise control, for example, automatically regulates the speed of a vehicles operation to a desired speed. Operation of the cruise control requires at least one glance away from the environment to set the desired speed. In addition, cruise control has limited utility in situations involving significant traffic where a steady cruising speed cannot be obtained. A head-up display is another effort to provide drivers information without requiring a diversion of attention away from the environment. These displays have found limited acceptance and use in practice, though. These two techniques also represent techniques which typically must be installed as original equipment, or added on at significant expense. This further limits their application in practice. Radar detectors notify drivers of the potential for detection by radar, which may cause drivers to pay more attention to the speed display used in a vehicle. This similarly causes a look away from the environment. In addition, the radar detector becomes an additional distraction if the vehicle speed is below a legal speed limit since the information provided by the radar detector in that case is irrelevant.
U.S. Pat. No. 3,980,041 to Evans seeks to provide an add-on speedometer speed warning indicator which could be applied to the clear cover of a speedometer without disassembly of the speedometer. The Evans device is a plastic plate which adheres to the cover of a speedometer such that once a critical speed is reached further acceleration of the vehicle will cause the needle in the speedometer to be hidden from view. Though this device obviates the need to disassemble a speedometer for use of the device, it fails to solve the problem of diverting an operator""s attention away from the vehicle""s operating environment. In addition, adjustment of the device is rather cumbersome since it requires removal of a plate and replacement with a differently configured, recut or repositioned plate.
Thus, there is a need for an add-on accessory which alerts an operator or a secondary device when a critical value is indicated by the output of an analog metering device without requiring the operator to look at the analog meter. Such an add-on accessory should be adjustable so that the operator may readily and conveniently select a desired critical value. Such a device is provided by the present invention.
The present invention is a self-contained accessory for an analog metering device such as a speedometer or tachometer. The accessory mounts to the clear cover of a metering device through adhesive, suction, or other suitable means. The accessory includes a selectively adjustable sensor which can be moved to a plurality of positions corresponding to operational positions of the needle of the analog metering device. A user or another device aligns the sensor with one of the gradation marks of the metering device. A signal is generated when the needle becomes aligned with the sensor. The signal is transmitted to a secondary device separate from the device, and it may also be used to generate an alarm signal. An exemplary secondary device is a radar detector such as might be used in a motor vehicle. Another exemplary secondary device is central monitoring system that might be used to collect information concerning critical values for an analog meter in an industrial setting. The generated signal also might be used to generate an alarm, preferably housed in the self-contained accessory.
The housing for the accessory is small enough that it doesn""t obscure the information contained on the face of the metering device. The housing includes a power source and the alarm which is responsive to the sensor. Preferably, the sensor is mounted on a rotationally adjustable arm that extends from the housing. In the preferred embodiment, the signal generated is transmitted wirelessly to a remote secondary device, e.g., a radar detector or central monitoring system.
A radar detector as a secondary device cooperating with an add-on accessory of the invention may use the signal to activate. In general, the radar detector uses the signal to effect a modified operation where at least some functions of the radar detector are responsive to the signal of the accessory. The radar detector is conventional, but is modified to use the signal to, for example, enable its alarm response from an alarm circuit or enable its detection function from a detection circuit. This can provide a method by which the radar detector conserves power and provides no irritating false alarms when vehicle speed is below a critical value. The radar detector would also have reduced susceptibility to VG-2 detection, which is used to identify the use of radar detectors. Such a radar detector or alternate secondary device, modified to accept and make use of a signal from an add-on accessory of the invention forms a second aspect of the invention.